In a hydraulic installation, where a forced flow of water passes through a hydraulic machine (of the type rotating turbine, pump or pump-turbine), the monitoring of sediment concentration in this water flow is of vital importance, as it originates abrasion phenomena in the hydraulic machine. In particular, sediment concentration is a key factor for hydro power projects that are located in rivers with high content of abrasive silt. As an example, the silt (sediment) content in a river flow during the flood season can go up from 100 mg/l to 10 g/l or even more. In spite of massive construction of de-silting basins provided, silt is moving ahead in the water flow; such high content of silt enters in the underwater hydraulic machine parts at significant speed of 20 m/s to 150 m/s, leading to severe abrasion and erosive wear in the cited hydraulic machine parts. Due to continuous impingement of silt onto the hydraulic machine parts being under water, erosion damages and changes the hydraulic profile of these underwater parts.
In order to mitigate this damage, abrasion resistant protection is applied on the hydraulic machine parts located under water, in order to enhance service hours. Moreover, at most of the sites, power plant operators shut down the hydraulic machine when a specific threshold silt concentration is reached. Hence, measuring the concentration of silt or sediment plays a significant role in the operation of a hydraulic machine.
At most of the hydraulic power plants, sediment concentration measurement in the flow is made by manual weighing of the flow passing through the machine comprising sediments, which is compared to a clean water sample used as reference. Although this method is reliable and accurate, it is also very cumbersome, time consuming, expensive, and the results are not available quickly, requiring very often weighing in order to provide a more continuous measurement of the sediment to establish a proper record.
It is known in the state of the art, as per U.S. Pat. No. 6,466,318 B1, for example, a device for measuring the diameter and area of particles in a given volume, by means of a submersible laser scattering instrument. A beam of laser light is directed across a void where a sample of water containing particles is admitted. After passing through the water, the light which is forward scattered out of the direct beam falls on two detectors at the same time, providing two measured outputs that, when electronically combined, give a mean diameter for the measured particles. However, such a system works on a sampling basis, which is not truly a continuous measurement. Moreover, this device can only work to a limit of 1000 mg/l: for higher concentration it may require dilution that may admit uncertainties in the measurement and a high pressure feeding of the system is not possible, as a local high water speed of erosive water would damage the system.
Therefore, it may be beneficial to develop a hydraulic installation where the measurement and monitoring of the sediment concentration in the water flow circulating through said hydraulic installation is done accurately and continuously.
Embodiments of the present invention are oriented towards providing such a hydraulic installation, and also to a method for operating such a hydraulic installation.